The Kermanshah ophiolitic complex (Zagros belt, Iran): A key area for understanding the geodynamic evolution of the eastern Tethys.

The Kermanshah ophiolites (KO) crop out along the Main Zagros Thrust and consist of an ophiolitic mélange including several rock-associations that record the geodynamic evolution of the Tethys between Arabia and Eurasia continental margins. Mineral and whole-rock chemical and isotopic data allowed the recognition of the tectono-magmatic significance of the different rock-types forming the KO, which are: 1) Exhumed subcontinental mantle lherzolites and associated gabbros and basaltic dykes that testify for a Triassic, asymmetrical continental break-up. 2) Pillow lavas ranging from alkaline basalt to P-MORB and E-MORB, which record the Late Triassic volcanism associated with plume effects occurring at the continent-ocean transition zone. 3) Foliated gabbro sequences (with N-MORB signature) and depleted lherzolites representing the conjugate magmatic rocks-mantle residua formed in a mid-ocean ridge setting during the steady-state spreading phase (Late Triassic- Late Jurassic). The residual MOR mantle was subsequently trapped in a SSZ and enriched in LREE by subduction-derived fluids. 4) Depleted harzburgites representing the residual mantle formed by multi-stage melt extraction (10-20% MORB melt + 25-30% boninite melt), which testify for the existence of an intra-oceanic arc associated with the consumption of the Tethys by a NE-dipping subduction (Late Jurassic). These data suggest that the eastern Tethys was characterized by rifted margins “intermediate” between the two ideal end-members: volcanic rifted margins (E Greenland-type) and non-volcanic rifted margins (Iberia-type). In fact, it was characterized by pulsed, asymmetrical rifting (like Iberia-type) and volcanism associated with plume effects (like E Greenland-type)